1. Field of the Invention
This invention relates to stacking amount detection control of a delivery processing apparatus coupled to a recording apparatus and, more particularly, to a delivery processing apparatus accurately detectable of a delivery stacking amount according to sheet delivery modes and to an image forming apparatus having this delivery processing apparatus.
2. Description of Related Art
Image forming apparatuses such as printers conventionally include a delivery processing apparatus for delivering plural image-formed (or recorded) sheets upon processing the sheets such as stapling where each edge is aligned. Such a delivery processing apparatus is formed on a top face or a side face of a sheet delivery outlet side of an image forming apparatus body, and a type of such a delivery processing apparatus has been known as the sheets on which recording is made at the side of the image forming apparatus body, are fed sheet by sheet from the delivery outlet to align each edge and to be delivered upon subjecting to processing the sheets.
Those delivery processing apparatuses tend to be formed with a mechanism detecting a stacking amount of the post-processed sheet bundles, and a control is frequently made as to suppress the sheet delivery to the delivery processing apparatus particularly when the stacking portion is made full.
When the sheet bundles subject to the sheet processing such as a stapling are stacked, however, proper stacking may not be performed due to rising only at the stapled portion. Under such a situation, the stacking amount detecting means located at the stapled portion likely detects as a fully stacked state even though the full stacking is not detected, thereby resulting disturbance of conveyance of the subsequent sheets.
To solve this problem, it may be required to form the stacking amount detecting means at the center as well as at the stapling position. Where stapling is made at an edge of the sheets, however, the stapling position tends to be near the alignment position of the sheet bundles, so that the operation ranges of the alignment mechanism and the stacking amount detecting mechanism inevitably interfere with each other, and so that the image forming apparatus may not operate with proper alignment operation and proper detection of the stacking amount.